Method of fixing nitrogen.



Jl E.v BUCHER. METHOD 0F FIXING NITROGEN.

APPLIATION FILED AUG. 8, 1911. 1,1 13,598. Patented Oct. 13, 1914.

UNITED s'rATEs PArENT clinica.

JOHN E. BCHER, OF COVENTRY, RHODE ISLAND, ASSIGNOR T0 NITROGEN PRODUCTS COMPANY, A CORPORATION OF RHODE ISLAND.

METHOD OF FIXING NITROGEN.

misses.

Specification of Letters Patent.

Patented Oct. 13, 1914.

Application led August S, 1911. Serial No. 642,918.

To all wzomz't may concern.'

Be it known that I, JOHN E. BUcHER,-a citizen of the United States, residing at Coventry, in the county of Kent and State of Rhode Island, have invented certain new and useful Improvements in Methods of Fixing Nitrogen, of Which the following is a full, clear, and exact description. I

This invention relates in general to the fixation of nitrogen and more particularly to an improved process for producing amino-nia, With the formation of commercially valuable byproducts incident thereto.

The process in question is c clic in character and involves the electro ytic produc'- tion of a metal capable of combining With free nitrogen to form a nitrid froma salt of' -then reacting upon the nitrid so formed with a suitable reagent to form ammonia or a compound thereof and preferably to re-form the original salt. The energy consumed 1n fixing the nitrogen is, hence, for the most part that employed in the electrolytic step of the process and it is desirable that a salt of such character be used intheqinitial operation as will readily yield to electrolytic action With a minimum expenditure of elec tric energy and aiiord a lmetal readily capable of forming a nitrid. lith such a metal as calcium or magnesium, the nitrid may be formed at a temperature approximating a dull red heat, and hence such metals are of special value in connection with my process. T ie haloid salts are preferred for use in the initial step of my cyclic process, and the nature of the by-product or by-products soughtwill determine Whether a chlorid, bromid, iodid, or a mixture thereof shall be used.

Many attempts have been made to utilize the chlorin of common salt, used'in the ammonia-soda process, for producing bi-carbonate and carbonate of soda. Solvay and Mond made many experiments with this end -in view but up to the present time none have proven economically successful. The common practice of today allows all of thevundecomposed common salt, Which amounts to about 30 per cent. of the total quantity used, and much of the chlorin of the decomposed salt to go to Waste, some of the chlorin combined with calcium being recovered and utilized as calcium chlorid. l

My invention renders possible the saving and utilization of all of the .undecomposed common Salt, and -substantially all of the chlorin of the salt which becomes decomposed, While furthermore'resulting in an increase of approximately one third of the quantity Vof ammonia present in the cycle.`

The manner of conducting my process in..

volatile ammoniais collected by brinein the.

usual manner a residue consisting essentlally of a mixture of dry ammonium chlorid l"and sodium chlorid being obtained. This mixture is then heated to the subliming` point of ammonium chlorid, to Wit, about 300 C., and the-ammonium c'hlorid is condensed to a solid sublimate leaving the sodium chlorid behind in an especially pure condition, suitable for any use, such as table salt, or for strengthening the brine used in the ammonia-soda process; While all of the ammonia corresponding to the decomposed sodium chlorid is thus recovered in the form of dry ammonium chlorid. The ammonium chlorid is then brought into contact with a nitrid at the lproper temperature, usually a dull red heat. Many nitrids are capable of reacting With ammonium chlorid, in practically all cases avith evolution of heat, producing ammonia or ammo-nium chlorid and achlorid'of the metallic base of the nitrid. For example, calcium nitrid reacts, in this connection, as follows:

The reaction in v this case evolves sufficient heat to maintain itselfafter it has once been started, and if moisture be excluded,

which is preferable, the reaction takes place A characteristic property of nitrids of the -metals andimetalloids-lithium, magnesium,

calcium, barium, strontium, alummum, s111- con, etc., and of boron nitrid, 1s the1r power 5 to decompose water atthe ordlnary, or at more or less elevated temperatures, as the case maybe, to form gaseous ammon1a,vand a hydroxid or oxid of the metal or metalloid. This method of producing ammoma is not economical because the oxid or hydroxid remaining has little value as such, and must be reducedto the metallic state before it can absorb nitrogen to re-form the nitrid, and it is very much more diiiicult and expensive to reduce the oxids and hydrox1ds of the nitrid forming metals than to reduce the haloids of said metals.

' I have discovered that not only do practically all of the nitrids react chemically with'the mineral acids, but that they also react with some other hydrogen compounds Y such as the acid salts, ammonium salts (an instance of which latter has been previously given), etc. As an example of such a reaction involving an acid salt, l may instance the formation of ammonia and magnesium carbonate, or oxid, according to the following equations;

a M aN ,renatico f 3 g 2 QNHHeMgcos-rauacd s) Mg-Nmmnoo: 3 NH,+3Mgb+soo2+eNa2oo,

while as further examples of reactions involving haloid salts, the base member of which is ammonium, I may cite:

The foregoing instances will serve to show the value and importance of the nitrids as used in connection with my process. As the process is cyclic in character, the method of re-forming the nitrid or nitrids used, from the haloid salt or salts produced as per the foregoing, may next conveniently be described. As intimated above, an electrolytic furnace of any well known type is employed inv this connection, the salt being .i fused at the proper temperature and being electrolytically decomposed, the base member being deposited out and the halogen constituent being liberated, usually in gaseous form. Mixtures of salts may be utilized in the furnace, as for example magnesium chloridsmay be mixed with sodium chlorid.

Further the magnesium or other metal may be separated as such, or it may be alloyed with a-heavy base metal such as lead, tin, antimony, or mixtures of these, or similar metals. In any case, the metal or metals whether deposited as such'or alloyed with other metals, must be capable of uniting with free nitrogen 5to form a nitrid or nitrids.

I have found it possible to use lithium, magnesium, calcium, strontium, barium, aluminum, titanium, and the metalloidssilicon and boron; but prefer to use calcium chlorid or magnesium chlorid as the haloid salts, because of the abundance and cheapness of these materials, and the particular facility with which they combine with nitrogen to form nitrids. owever, while I prefer calcium and magnesium, I do not confine myself to any particular nitrid forming element, nor to the use of any specific non- 8U metallic element or group of elements to combine with it, e. g., the iodids, bromids, oxids, or similar compounds which may be electrolyzed. The gaseous halogen given oil during electrolysis is in condition to be utilized in the usual ways, asby absorption with lime to form bleaching powder, or by compression and cooling to liquefaction. It may also be utilized for the production of oxygen, etc., by absorbing it in milk of lime in the presence of a catalytic agent.

Referring to equations l, 4, 5 and 6, it will be noted that the ammonium is therein, in each case, uncombined after the respective reactions have been effected. By supplying an excess of the halogen during the course of these reactions, a salt of ammonia may be formed. Thus if, for example, magnesium chlorid be electrolyzed, depositing metallic magnesium and liberating chlorin gas; this latter may be brought into contact with hydrogen, forming anhydrous hydrochloric acid, and this in turn may be caused to react with the magnesium nitrid formed from the deposited metal, thus:

(7) MgnNz-i-GHC/l:3MgCl,--2NH Using an excess of hydrochloric acid, the reaction is as follows:

Thus we may readily obtain a supply of the ammonium chlorid used as per equation 4; the magnesium chlorid being separated from the ammonium chlorid by sublimation 11b of the ammonium chlorid and the magnesium chlorid being then electrolyzed as above.

The metalfor alloy -produced simultaneously with the halogen isbrought into contact with pure nitrogen at the proper temperature, generally a red heat, producing a nitrid of the nitrid forming metal, which nitrid may then be utilized in the ways above set forth.

To summarize briefly the foregoing operations last mentioned: A haloid salt of a metal capable of forming a nitrid is electrolyzed to deposit the metal and liberate the halogen element of the salt. The gaseous halogen 130 may be utilized 'for various purposes but ls preferably treated with hydrogen to form an acid. The nitrid forming metal is united with nitrogen, and the so formed nitrid is treated with the acid aforesaid, yielding an ammonium-halogen compound and a haloid of the vnitrid forming metal. These salts lare' separated, in the manner above described,

(a) casN2+cHc1=2Nn8+soac12 Electrolysis of the so produced chlorid of calcium gives chlorin and calcium, and the former may be utilized as such, or may be used to form hydrochloric acid,4while the calcium may be converted into calcium nitridto be reacted upon by hydrochloric acid. My process is hence adapted to any industry wherein hydrochloric acid is available or wherein it may be produced.

The cyclic process may also be carried out in other ways, e. g., water may be used and anhydrous ammonia obtained, as is shown by the following equations:

The oxids so produced, can then be converted into chlorids by methods such as are set forth in the following equations:

Upon heating, the calcium compound loses its oxygen content, thus:

(14.) 2oaoo12+hea=coac12+o2- f completing the cycle. Also the magnesiumv '(16) MgO-l-2HCL- Mg 12+H2O completing the cycle. Or the magnesium to re-form'the magnesium chlorid, thus:

'completing thecycle.

The carbon monoXid of equation 12 may be converted into carbon dioxid by burning it in oxygen or air. In the latter case free nitrogen may be obtained by absorbingthe carbon dioxid in any of the Well known manners, and this free nitrogen may be-.converted into ammonia in the manner above described, while the carbon dioxid may be used in the carbonating towers of the ammonia-soda process. That it is thus possible to form pure carbony dioxid in connection with said process is of great value, since it renders possible the use of smaller carbonating towers, thereby increasing the eiliciency of production as a whole. The waste nitrogen of the ammonia-soda industry from the carbonating towers may also be used in the above cyclic process. From an economic standpoint therefore my present process is admirably adapted to supplement many now in use, or it may be operated to advantage independently.

In view of the variety of applications to such element; while the term light metal is intended to embrace such metals as the alkali metals, alkaline earth metals and aluminum.

In the accompanying drawing which vforms a part hereof I have shown suitable apparatus in which my novel processs may be effectuated. It is obvious however that this is only by way of eXempliiication and I do not desire `to be limited thereto in any particular.

Referring to -said drawings: Figure l is a vertical cross-section of an electrolyzing apparatus wherein the salt of the nitrid forming metal, e. g. magnesium chlorid, may be dissociated to liberate said metal. Fig. 2 is a somewhat diagrammatic representation of a reaction tube or retort wherein the nitrid forming metal may be reacted upon with a nitrogenous reagent to form a nitrid. This reaction tube further serving, if desired, as a receptacle wherein to effect other reactions involved in the process.

In Fig. l, the pot or receptacle 1, may be Similarly I regard the of iron or other suitable material, and conject the positive poleI electrode- 3 land the; negative pole "electrode 4:" These latter. may

be of any suitable description and material o r materials. The electrode 3 is preferably incl'osed in' "art atleast by a tube or pipe 5,v of iron or example,'which should .be lined with a protectivelining 6, 1 of porcelain, vlfor example-a` Theelectrode '4, of course, need not-beysoprotected." When direct current is passed through.A the bathfrom.

`3 tol 4, thesalt' of-'Which the bath-.is composed.willnbevdecomposed, chlorin, for example, beingliberated'at the electrode 3 and 4thence escaping ythrough the tube 5; while, themetal e. g. magnesium, will rst be die-r posited at or'adjacent to ,the f electrode 4'. When. a suflicient quantity of the nitrid forming metalhas been accumulated it may ,be:.withdrawn from the cell 'orpot- 1 via thel pipe 7. The pot is provided .vv-ith Aasuitable cover 8, which should be air tight,- and the electrode-4 may be insulated from. thisy cover by an insulating bushing 9. The metal Withdrawn from pipe 7 may be introduced into the reaction tube 10, which latter may be heated in-.any suitable manner as by a number of B unsen burners 11. The sodium 12, for` example, i'n the retort or--reaction tubefis converted to a nitrid by passing nitrogen or a.- suitable nitrogenous reagent,

e. g., free nitrogen, through-the tube, suchY reagent passing thereintmfrom a tube orv pipe 13,' andthe unused portion of the same escaping via tube.l4. Cocks' or valves 15 may be provided in these last mentioned pipes. The halogen, e. g., chlorin, escaping from lpipe-5,- is collected and may be combined With hydrogen, for example, to form hydrochloric acid; and when the nitrid of magnesium, for instance, Ain tube 10, is reacted upon With said acid, which may be introduced into 'said tube in any suitable man-- ner, asv/by injection, at a stage in the processsubstantially as previously described, (equations 7 and 8'), ammonia formed may escape through tube 14: While the resulting reformed haloid salt' will remain in the reaction tube, from'which it may be afterward `removed 'preparatory toa gain electrolyzing the same.`

Having described my invention, I'claim: 1. The cyclic method ofpxing nitrogen vvhich comprises electrolyzing a haloid salt .of a metal capable `of forming a nitrid, re-l acting-upon the said electrolytically sepa? of a metal capable ofjfornng ainitrid, rel acting -upon' 'the said' electrolytically separated metal witha' nitrogenous rea ent to vform a nitrid, and treatingisaid nitrid with a; fhydrogen-halogen compound toform a substance cornprisinganimoniafand to reform the haloid salt above-referred vfto.'

vv3. The cyclic .method of fixingv nitrogen which compriseselectrolyzing a haloid salt 4vof a metal capable offorminga nitrid, re-

.acting upon the sail'delectrolytically sepa-- ferred to, and separating s'aid substance com- V prising ammonia from `the said salt.

5. The method of fixing,l nitrogen which comprises electrolyzing a saltof a metal capable of forming a nitrid, reacting upon the said electrolytically separated metal with a nitrogenous reagent to'form a nitrid, treating said nitrid' with an ammonia-halogen `compound to form ammonia and a halogen salt of the-metal above referred to.

6. The method cfg-fixing nitrogen which comprises electrolyzing a 'saltof a metal capable of forming a nitrid, reacting upon the said electrolytically separated metal with a nitrogenous reagent to form a nitrogcnous compound, treating said nitrogcnous compound with asubstantially anhydrous hydrogen` compound capable ofreacting therewith to form ammonia and alsoa salt of the metal 'above referred to.

7. The method of* fixing nitrogen which .L

'comprises reacting with a hydrogen halogen compound' upon the nitrid of an element which is capable of combining With nitrogen at a temperature not exceedin a red heat, thereby 'forming'an ammonia- 'alogen .compound and also a halogen compound of the element aforesaid, separating the. last 4mentioned compounds from one another by sublimation, and-treating the halogen' compound of the nitrid forming element to reform the nitrid aforesaid'.

8, The method of firing nitrogen which comprises reacting with a substantially anhydrous hydrogen compound upon lthe nitrid of a light metal, to form a substance comprising ammonia and also a saltvof the nitrid formingA light metal., and separating said substance from said saltfb .,sublimation.

9. The method of fixing -nltrogen which comprises reacting with strong'hydrochloric acid upon the nitrid of a light metal, capable of reacting therewith to form a substance comprising ammonia and also a salt of the nitrid forming light metal and separating said substance from said salt.

10. The method of fixing nitrogen which comprises electrolyzing a haloid salt of a metal capable of forming a nitrid, reacting upon said electrolyticallyv separated metal with a nitrogenous reagent to form a nitrid, and treating said nitrid -to form a nitrogenous compound and to form a haloid salt of said metal, said treatment including reacting upon said nitrid with a reagent capable of yielding a substance containing nitrogen in combination with an element 'having a lower atomic weight than nitrogen.

11. -The method of fixing nitrogen which comprises electrolyzing a haloid salt of a metal capable of forming a nitrid, reacting upon said electrolytically separated metal with a nitrogenous reagent to form a nitrid, and treating said nit-rid to form a nitrogenous compoundand to form a haloid salt of said metal, -said treatment including reacting upon saidnitrid with a reagent capable of yielding said nitrogenous compound by a direct reaction.

12. The method of fixing nitrogen which trolytic action, reacting on said liberated haloid with a reagent toform a halogen acid, treating said nitrid with said acid to form a substance comprising a nitrogenous compound and `to form a haloid salt, and separating said substance fromsaid salt.

13. The method of fixing nitrogen which comprises electrolyzing a salt o? a metal capable of forming a nitrid, reacting upon the said electrolytically separated metal vwith a nitrogenous reagent to form a nitrogenous compound, treating said nitrogenous compound vwith asubstantially anhydrous compound capable of reacting therewith to form a substance containing nitrogen in combination with .an element having a lower atomic wei htthan nitrogen and t0` also form a salt o the metal above referred to.

14. The. method of Afixing nitrogen which comprises reactingfwith a substantially anhydrous hydrogen compound upon the nitrid of a light met-al, to form a substance containing nitrogen in combination with an element having'a lower atomic weight than nitrogen and to also form a salt of the nitrid forming metal, and separating said substance from said salt by sublimation. e In witness whereof, I subscribe my signature in the presence of two witnesses.

JOHN E. BCHER. Witnesses:

CHARLES A. CoMMINs, J. WALTER SCHNEmER. 

